Centrifuge with sample holding means for sedimentation study

ABSTRACT

An improved centrifuge apparatus for blood sedimentation study is described for applying a G force in the range of 6.25 to 8 G laterally to the long axis of plural test sample columns arranged substantially vertically in holders provided on the centrifuge head. Each of the sample columns are rotated about their own vertical axes between each periodic spin cycle of said centrifuge head and only between applications of said G force by means of inertia. A test operation using four 45 second duration applications of said G force is described with rotation of the columns being effected by reversal of the centrifuge head at the end of each 45 second force application.

ted States Patent Proni Oct. 30, 1973 CENTRIFUGE WITH SAMPLE HOLDINGMEANS FOR SEDIMENTATION STUDY Primary Examiner-George H. Krizmanich [75]Inventor: Oscar Proni, Hollywood, Fla. Attorney-I Irving Sllverman et [73] Assignee: Coulter Electronics Inc., Hialeah, [57] ABSTRACT Animproved centrifuge apparatus for blood sedimen- [22] Filed: O t, 22,N71 tation study is described for applying a G force in the range of6.25 to 8 G laterally to the long axis of plural [21] Appl' 19l768 testsample columns arranged substantially vertically in holders provided onthe centrifuge head. Each of 52 US. Cl. 233/26, 23/259 the Samplecolumns are rotated about their own verti- [51] cal axes between eachperiodic spin cycle of said cen- [58] Field of Search 23/259; 233/24, 23R, trifugo head and y between applications of Said 6 233/23 A 25 2 17; 20 335 force by means of inertia. A test operation using four 45 secondduration applications of said G force is de- [56] References Citedscribed with rotation of the columns being effected by UNITED STATESPATENTS reversal of the centrifuge head at the end of each 45 3,199,7758/1965 Drucker 233 25 Second force apphcanon' 749,104 1/1904Schoenefeldt 233/17 13 Claims, 5 Drawing Figures 11 27 "Elm" PATENIEnucI30 1975 3,768,727

sum 1 UF 2 CENTRIFUGE WITH SAMPLE HOLDING MEANS FOR SEDIMENTATION STUDYCROSS-REFERENCE TO RELATED APPLICATION This application is animprovement of the centrifuge disclosed and claimed in co-pendingapplication of Brian S. Bull, Ser. No. 191,886, filed Oct. 22,1971entitled METHOD AND MEANS FOR SEDIMENTA- TION STUDY and assigned to acommon assignee.

FIELD OF THE INVENTION This invention relates generally to diagnosticexamination of whole blood and more particularly concerns the provisionof a centrifuge for whole blood sedimentation study.

BACKGROUND OF THE INVENTION It is well known that the suspensionstability of whole human blood is altered in the presence of manyfunctional disorders. The determination of this characteristic generallyhas been effected by performance of wellknown standardized sedimentationtests in the course of clinical analysis. Using the sedimentation testresults, the presence of more or less occult disease can be brought tomedical attention. Such results particularly are of importance in thedifferential diagnosis as between functional disorders having closelysimilar symptomatic manifestations, as well as in supplying a guide tothe progress of certain diseases. Accordingly, it is believed thatsubstantial benefit could be obtained in the diagnosis and treatment ofmedical disorders by the establishment of sedimentation study procedureswhich would produce comparative information quickly and economically sothat a sedimentation study could become a routine procedure in clinicalexamination. However, as practiced presently, the sedimentation test istoo time consuming, too affected by laboratory introduced artifacts andsubject to misinterpretation in anemic individuals, so that the test isnot a test offered to every patient as a routine clinical test proceduresuch as a blood count, for example.

Present methodology involves essentially the mixing of a whole bloodsample with a selected anticoagulant, introducing this well mixed samplein a vertically arranged glass tube and permitting the red cells of thesample to sediment under the influence of gravity. This process is slow,usually taking sixty or more minutes. The only accepted variations inthis method takes the form, singly or in combination, merely of changingthe length of the glass tubes employed, varying the bore of such tubes,careful selection of the anticoagulant employed and/or modification ofthe degree of dilution utilized. None of these variations havealleviated the principal drawback to adoption of the sedimentation testas a routine procedure, this drawback being that present sedimentationrate tests methods are too time consuming for routine employment or massstudies.

Another important deterrent to adoption of sedimentation testing as aroutine procedure has been the extreme sensitivity of this test to thearrangement of the test sample in an absolutely vertical orientation forthe duration of the test. It has been found that a sample column whichis oriented at only a three degree offset from vertical will result ininconsistent acceleration of the sedimentation rate and reduces therelative differences between the comparative normal and abnormal bloodsedimentation characteristics, thereby reducing the value of the test indiagnosis.

The co-pending application provides an improved sedimentation studymethod for whole blood which meets the requirements for rapidity,economy, accuracy and reliability essential for adoption as a massapplied clinical laboratory test procedure, and, concomitant therewith,provided a sedimentation rate centrifuge particularly adapted forimplementing and carrying out the steps of the improved study method.

The principal object of this invention is to provide an improvedcentrifuge for blood sedimentation study particularly adapted for usewith the method of the aforementioned application.

SUMMARY OF THE INVENTION A centrifuge apparatus is provided forimplementing the subject method, including a centrifuge head and areversible direction motor, the centrifuge head carrying at least a pairof sample tube holders arranged to orient sample columns carried inelongate tubes held in substantially vertical columnar array, drivemeans connected between the motor and the centrifuge head for rotatingsame, means associated with the head and tube holders, rotating the tubeholders about their own vertical axes and timing means operable on saiddrive means for operating the centrifuge head in timed cycles with thecentrifuge head being brought substantially to a rest condition betweencycles and means to restrict the rotation of the tube holders abouttheir own vertical axes to periods during which the centrifuge head isat substantial rest condition, said drive means including a first gearmeans coupled to said motor, second gear means coupled to said tubeholders and the said centrifuge head, said centrifuge head being mountedfor free rotation about the drive shaft axis, said means to restrictcomprising pin and slot means on the first gear means and centrifugehead, said first gear means transmitting its motion to said second gearmeans for first rotating said tube holders about their own axes, saidmeans to restrict serving to couple said centrifuge head and first gearmeans for simultaneous rotation subsequent to said rotation of said tubeholders.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of theimproved centrifuge apparatus in accordance with the invention;

FIG. 2 is a perspective of the centrifuge head and drive means of thecentrifuge arrangement of FIG. I with portions broken away to showinterior detail;

FIG. 3 is a diagrammatic representation of the embodiment illustrated inFIG. 1;

FIG. 4 is a bottom view of the timing means utilized in the embodimentof FIG. 1;

FIG. 5 is a schematic view of the centrifuge head of the embodimentillustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of studying thesedimentation characteristics of whole blood described in the co-pendingapplication capitalizes in part upon the fact that the blood from anormal, healthy individual has greater suspension stability than doesblood from a sick individual. Three phases are known to occur during thesedimentation of whole blood. The first packing characterized as thephase of rouleaux formation. During this phase, the

red cells of the whole blood stack together in what is defined in theart as rouleaux. This phase occupies the first few minutes subsequent tofilling of the sedimentation tube with sample. Next begins the phase ofmaximum sedimentation wherein about 3 to 5 minutes, the red cellrouleaux reach their maximum velocity of fall. This velocity is dictatedby the average density of the rouleaux and the viscosity of the plasmathrough which they are falling. The last phase concerned ischaracterized as the package phase. As the rouleaux reach the bottom ofthe sedimentation tube, they pack and, as a consequence, the averagerate of fall decreases and eventually, when packing is complete, nofurther change occurs.

The sample from both normal and sick individuals, given enough time,will pack to approximately the same extent; but the blood samples fromthe ill patient goes through the rouleaux formation phase and into thephase of maximum velocity of fall more rapidly than does the blood froma healthy individual. An isolated red cell is so small a particle thateven through its density is considerably greater than that of theplasma, the large relative surface area becomes the overriding factorand an isolated red cell in plasma falls very slowly under the influenceof gravity. The rate of fall of red cells is thus governed almostentirely by the size of the rouleaux which they form. The blood from a.healthy individual forms such rouleaux much more slowly than does bloodfrom a sick person. If both samples are set up simultaneously, there isa period of time when application of force greater than gravity to theblood will affect the blood from a healthy individual minimally and thatfrom a diseased patient maximally. This crucial or critical time isobvious when the healthy blood has just only begun to form rouleaux andthe sick blood has formed large rouleaux which have already begun tosediment.

lt had been critical to the study of sedimentation rate that theconventional test must be performed under conditions where the samplecolumn is disposed in absolutely vertical orientation. A tilt as littleas three degrees from vertical under gravity will accelerate thesedimentation rate considerably, and decrease the relative differencesbetween normal and abnormal blood. It is believed that this effect isdue to the fact that red cells falling through the plasma hit the wallsof the container and roll down the walls permitting the plasma freeegress from the depth of the sample. Whenever the plasma is forced totraverse the descending column of red cells, the sedimentation rate isslowed. Normal red cell rouleaux fall much more slowly than do abnormalred cell rouleaux, probably because the forces holding them together areweaker and the upsweeping plasma either breaks them up or prevents themfrom forming large enough clumps to sediment rapidly. Accordingly, byapplying a greater than gravity force to the sedimenting blood,according to the method, the ascending plasma is forced to traverse thedescending red cells. As will be explained, a slight inclination of thecolumn up to about 6 from vertical is permissible with the method of theinvention, particularly to avoid spilling of the sample during the run.

According to the method, greater than gravitational force is appliedlaterally to a long thin column of whole blood sample by rotationthereof in a centrifuge capable of delivering a force in the range of 2to 12 G with the test taking fron Ar hour at a minimum (3 to about 1minute at the high end of the aforesaid range. The higher the G Force,the shorter the elapsed time of the test. The net effect is to force thered cells to traverse the plasma component of the blood over a veryshort distance since the effective cross-sectional area of the tube isnow vast relative to the wall surface area and the red cells cannotcollect in one portion of the tube against the wall so as to permit theplasma to escape freely elsewhere. insofar as the sedimentation processis concerned, the long thin column has been transformed to a shallowwide diameter pool and since the force is directed substantiallyperpendicular to the long axis of the column, the problems of channelingheretofore experienced in sedimentation testing are obviated.

The laterally applied force acts to pack the red cells rapidly,permitting the plasma physically to change location therewith andapproach the final packing state over a much shorter time period, thannormally would be expected under gravitational force.

The selection of the duration of the centrifugation cycles as well astheir number are dependent also upon the speed of the drive orsynchronous spinner motor utilized, the diameter of the column and ofthe sedimentation tube utilized, and the degree of cant or tiltpermitted.

A preferred program involves a program selected to use four cycles ofapplied force laterally to the column and of 45 second duration each.Between the first and second, the second and third and the third andfourth cycle of centrifugation, the columns are rotated about their ownvertical axes. Care is taken to assure that the axial rotation of thecolumns take place only when the force applied laterally to the longaxes of the columns is less than one G. This condition occurs when thecolumn is at rest. substantially at rest or, to put it another way,beings its translation in its circumferential rotation with and on thecentrifuge head. Abrupt stoppage of the columns must be avoided, andlikewise, jarring or other sharp disturbance of the columns are avoidedso that the cells which have separated from the plasma and gathered atthe inner wall of the tube containing the test sample column will not bebroken away from each other or from the tube wall. The cells in thecolumn must rotate with the tube, and the column as the same is rotatedabout its own axis. Between each application of greater than gravityforce, the test sample column is rotated about its own long axis,preferably This seems to provide benefical results in obtainingreproducible packing by alternatively permitting resuspension of thecells by rotating the tube and its column contents and again effectivelyforcing those cells back through the plasma. Thus, cohesive forces areutilized during the centrifugation under the relatively low G force toforce the cells against the wall and dispersion forces are utilized whenthe cells are forced back through the plasma by again centrifuging butafter 180 rotation of the tube and column of test sample.

The performance of the method described and claimed in the co-pendingapplication required a centrifuge capable of applying the preferable Gforce in the range of 6.25 to 8 G in separate cycles of predeterminedduration. The centrifuge is required to rotate the tube containing thesample in a circumferential path about the axis of rotation with thetube being in substantially vertically oriented disposition parallel tothe axis of rotation of the centrifuge head although a cant fromvertical of up to 6 is permitted, contrary to standard sedimentationrate methods. Additionally, the centrifuge is required not only topermit rotation of the tube along said circumferential path for apredetermined length of time and then the tube periodically must bebrought at least to a momentary substantially rest or stationarycondition, then rotated about its own axis a predetermined number ofdegrees, and the rotation of the tube along said circumferential pathresumed for the next cycle of greater than G force application. Atleast, the rotation of the tube about its axis must not occur during theapplication of greater than G force.

The centrifuge also should have timing means T for selectivelycontrolling and/or varying the duration of the cycles. The columncontents of the sample tube must rotate axially with the tube wall andcare must be taken to assure only such rotation.

The centrifuge apparatus according to the instant invention isillustrated in FIG. 1 and designated by reference character 101).Apparatus 100 as described herein particularly is adapted to practicethe subject method where the cycle utilized comprises four cycles of 45second duration applications of greater than gravity force laterally tosubstantially vertically arranged columns of whole blood with meansprovided to effect limited rotation of each column about its own axisbetween each force application by reversal of the direction of rotationof the centrifuge head after each cycle.

The centrifuge apparatus 100 includes a housing 102, including atroughlike portion 104 and a cover 106. Wall 108 of housing 162 carriesexterior accessible switch levers 110 and 112 for activating the powerand buzzer means respectively which will be described hereinafter.Indicator lights 114 and 116 likewise are provided. Start switch 11% forinitiating each test operation is provided.

The electrical control components of apparatus 100 are mounted withinthe troughlike portion while the head, centrifuge 120, drive means 122,and the timing means 124 are mounted on the cover portion, thecentrifuge head being removably mounted to the protruding portion of themotor drive shaft 154 of means 122. The drive means 122 and timer means124 are mounted to be enclosed within the housing 102 when the cover1116 is engaged onto the portion 104.

The centrifuge head 120 comprises a spool formed by mounting a spinnerplate 126 fixedly secured to the shaft 128 and a disc 130 is mounted tothe upper end of said shaft 128 with the disc 130 arranged coaxial withsaid spinner plate 126 and being rotatable therewith to complete thespool. The shaft 128 is mounted removably on the motor drive shaft 154for free rotation about the axis thereof.

Support means 132 is arranged secured to drive shaft of motor 156 forrotation therewith by set screw 127 and includes a collar portion 192mounting a spur gear 134. Gear 134 has a circumferential ring portion134 carrying circumferential teeth 134" and a central disc portion 135to which it is fixedly mounted and by which the spur gear is mounted fordriven rotation with the shaft 154. The shaft 128 has a dependingextension 123' and carries a bottom opening axial bore 128" by whichspool 121) is mounted on shaft 154 for free rotation thereabout. (seeFIG. 5)

Tube holders 136, are mounted on spinner plate 126 for movementtherewith about the axis of shaft 128.

The holders are spaced circumferentially substantially equidistant onerelative to the other closely adjacent the peripheral edge of thespinner plate 126. Each tube holder 136 has a top opening cavity 137defined therein to receive the lower end of sample tube 150 and hasresilient means for gripping said tube seated therein, such as O-ring139. Each holder is mounted on the upper end of a shaft 138 whichextends through suitable openings formed in said plate 126. Pinion gears141) fixedly are secured to the opposite ends of each shaft 138 therebymounting the holders 136 on plate 126. The holders 136 are rotatablewith rotation of gears 140.

The teeth 134" of spur gear 134 are arranged meshed with the pluralpinion gears 140. Thus, rotation of the gear 134 will effect rotation ofgears 140 while the plate 126 remains stationary, rotating holders 136about their own vertical axes. Limit means in the form of the upstandingpin 142 secured to the disc and movable within the substantiallycircular slot 144 formed in the spinner plate 126 are provided to limitthe independence of movement of the spinner plate 126 and gear 134,thereby limiting the degree of rotation of the gears about their ownaxes. With the pin 142 at one end of the slot 144, the rotation of gear134 in the direction of arrow A will cause simultaneous rotation of theplate 126 and hence the tube holders will be translatedcircumferentially about the axis of shaft 154. On completion of thefirst cycle, gear 134 stops. The plate 126 stops with gear 134 or coastsuntil pin 142 is at the opposite side of slot 144. In changing directionof rotation of the plate 126, gear 134 rotates gears 141) until the pin142, moving in slot 144, engages the opposite end of the slot 144. Thenthe motion of the gear 134 in the opposite rotational direction istransmitted to the plate 126 and the gear 134 and head 120 rotatetogether. The tubes within holders 136 are always rotated about theirown axes before the head reaches sufficient rotational speed to applygreater than 1 G force laterally to the tubes.

The disc 130 has a plurality of bottom opening recesses 146 formedequispaced about the peripheral edge thereof and arranged in alignmentwith the axes of the holders 136 but slightly offset inwardly therefromso that one end of the sample tube 150 can be seated within cavity 137of holder 136 and the upper end retained within the respectivelymatching recess 146 to position the tube substantially verticallyarranged but canted inwardly at its upper end toward the shaft 128.Thus, when properly seated, tubes 150 are disposed, canted inwardly fromtrue vertical between 3 and 6, preferably by 3 and generally not morethan about 6. In this disposition, the tendency for the contents of thetube to be flung outward during the application of higher than gravityforce on rotation or spinning of the centrifuge head 120 materially isreduced.

Motor mount 152 is secured to the undersurface of cover 106 with thedrive shaft 154 thereof protruding through a suitable opening formed insaid cover 106. The drive means 122 for the apparatus 100 is supplied bya 400 RPM, 60 HZ, l 15 volt AC reversible direction motor 156. Here,motor 156 causes centrifugal force between 6 and 8 G to be appliedlaterally to the tubes 1511 during the spin of header 120. Theparticular size and RPM drive motor selected determines the centrifugalforce exerted on the tubes 150, and thereby is an important factor inselection of the duration of greater than gravity application cycle andprogram.

The method of study concerned requires application of the greater thangravity force laterally and periodically to the sample in the tube i.e.,the sample tube 150 and the column of blood therein. The duration ofeach cycle generally can be selected to provide results correlative withspecifically known blood sedimentation methods.

With apparatus 100, timer means 124 are provided to effect rotation ofthe spinner plate automatically through a sequence of four cycles of 45seconds duration with the reversal of direction and rotation of thecolumns 180 about their own axes between each application of centrifugalforce.

in the apparatus 100 illustrated, the timer motor 156 is an AC 60 cycle,1 10 volt motor delivering RPI-l.

The timing means 124 operates switch means 184, 186 which operatesrelays 184" and 186 automati cally taking the sample columns through theselected test program.

A timing means 124 comprises a timer motor 158 mounted on platform 159,which in turn is secured suspended below the cover 106 by means of bolts160 and spacers 162. The resultant drive shaft 164 of motor 158 ispassed through a suitable opening in the platform 159 and wheel gear 166is mounted at the free end thereof for rotation therewith. A secondwheel gear 168 is coupled to gear 166 and is driven thereby. Gear 168 isfixedly secured to shaft 170 for rotation therewith. One end of shaft170 is seated in journal 172 and the other end 174 carries timer disc176. Timer disc 176 is secured to shaft 170 and continuously rotatestherewith so long as timer motor 158 operates through the complete testprogram. The timer disc 176 has three paddle assemblies 178, 178 and178" mounted thereto about the periphery thereof with the paddles 180,and 180 and 180" extending outwardly from the circumferential edgethereof in vertical planes normal to the axis of shaft 170. Asillustrated, disc 176 is rotatable in the direction of arrow 177 withthe paddle assemblies 178, 178' and 178" fixed in an equispaced seriesalong said path. An upstanding pin 182 is secured normal to the disc 176and rotates therewith. The paddle assemblies 178, 178 and 178", whenconsidering the direction of rotation of the disc, can be said to besubstantially equispaced one relative to the others with paddleassemblies 180 and 180" being disposed 180 apart. A pair of push-buttonactivated switches 184 and 186 are arranged with their actuators 184'and 186 mounted to suitable bracket means (not shown) secured to theplatform 159 so that the actuator 184 of switch 184 is arranged in thepath of travel of the paddles 180, 180 and 180" of paddle assemblies178, 178' and 178" whereby each respective paddle can engage and depresssaid actuator 184' by engaging same during passage therepast duringrotation of the disc 176.

The actuator 186' of switch 186 is positioned to intercept the pin 182whereby the continuing rotation of disc 176 causes pin 182 first to bearagainst actuator 186 to depress same. On passing of said pin 180 pastactuator 186, said actuator returns to its normal condition. The switch184 is connected to relay assembly 184' which is electrically coupled tothe reversible sychronous drive motor 156 to cause reversing of thedirection of said motor each time the actuator 184 is depressed. Theswitch 186 is connected to relay assembly 186" operatively coupledelectrically to both the drive motor 156 and to the buzzer means 190.Depression of the actuator 186' energizes the buzzer 190 and release ofthe actuator 186' from engagement with the pin 182, causesde-energization of the drive or spinner motor 156.

A friction or other drag represented by pad 194 may be applied to thecentrifuge head 120 so that application of braking force to the motor156 on deenergization of the same, causes a braking force to be applieddirectly to the head.

An example of a testing operation utilizing apparatus now will bedescribed. Samples of whole blood are taken and placed respectively inclosed end, elongate tubes known as sedimentation tubes. The tubes arefilled with sample to a predetermined level mark. The tubes containingthe test samples are placed between the disc 130 and the spinner plate126, the lower ends of the tubes seated within the tube holders 136 andheld firmly by the resilient means 139 while the upper ends are seatedin the recessed holes 146. The switch levers and 112 are actuatedrespectively activating the apparatus 100. The start toggle switch 118is actuated initiating the test procedure and causing the spinner motor156 to operate in one direction, say clockwise. Greater than gravityforce in the range of 6.25 to 8 G is applied to the column of sample ineach tube as the centrifuge head 120 is spun.

When motor 156 is energized to spin gear 134, motor 158 is energizedsimultaneously to rotate disc 176. Timer disc 176 rotates to bringpaddle 180 in contact with the actuator 184. Disc 176 continues torotate so as to carry paddle 180 past said actuator 184. In passing, thepaddle 180 depresses the actuator 184', causing the spinner motor 156 toreverse direction. This occurs 45 seconds after initiation of thespinner operation.

In reversing direction, the gear 134 and hence the centrifuge head 120comes to a momentary halt with the pin 142 at one end of the slot 144.The gear 134 then begins to rotate in the clockwise direction. The plate126 will remain stationary. The pinion gears being coupled to the gear134, will move along the circumference of now moving gear 134 and willrotate about their respective axes until engagement of the pin 142 atthe opposite end of the somewhat circular hole 144 will drive the plate126 to rotate same, iimiting the rotation of the pinion gears 140 to180. The rotation of the pinion gears 140 rotates the tube holders 136and with same, the tubes and the column of blood sample will be rotated.

The spinner motor 156 operates to drive the gear 134 and head 120 in aclockwise direction for the next cycle of 45 seconds. At the elapse of45 seconds, the next paddle will have brought around to depress theactuator 184 and cause a second reversal of the drive motor 156. Thegear 134 again is brought to a momentary halt. The plate 126 stops withthe gear 134 or coasts until the pin 142 now is at the other end of theslot 144. The reversal of motor 156 rotates the pinion gears 140 180about their own axes until the pin 142 is at the opposite end of theslot 144 and hence before any appreciable centrifugal force has beengenerated.

On completion of the movement of the pin 142 in the slot 144, andengagement of said pin 142 with the spinner plate 126, the spinner plateand the gear 134 are locked for rotation together, now in thecounterclockwise direction for another 45 seconds until the spinnermotor direction is reversed by engagement of the paddle 180" against theactuator 184' of switch 184 depressing same. The pinion gears 140 andhence, the holders 136, tubes 150 and test sample columns therein, againare rotated about their own axes between applications of centrifugalforce by the inertia of the plate 126.

Coupled rotation of the spinner plate 126 and gear 134 is resumed foranother and final 45 second interval. The timer plate 176 iscontinuously rotating during these last described operations, and,accordingly, continues to rotate. Approximately 45 seconds after thelast-mentioned motor reversal, the pin 182 is brought into contact withthe actuator 186' by the continued rotation of the timer disc 176, theactuator 186 is released from its depressed condition. Now the motor 156is de-energized and the gear 134 and the centrifuge head is brought to ahalt, the program completed.

It should be explained that the centrifuge apparatus of the copendingapplication has means whereby a friction drag was applied to the spoolor head driven by the motor 156 with thegear 134 thereof mounted forfree rotation about the drive axis. Friction under some circumstancescan become unreliable, may change with time and/or may be different fromone unit to another. It is for this reason the inertial operation of theinstant apparatus is so advantageous.

In FIG. 2, a resilient or elastic belt coupling 141 is utilized betweenthe motor drive shaft and the main drive shaft (dotted line) which aidstaking the inertia load off the synchronous motor 156 while it isreversing direction, or at least most of it, making starting of themotor more reliable.

What it is desired to be secured by Letters Patent of the United Statesis:

l. A centrifuge apparatus for studying the sedimentation characteristicsof whole blood by application of greater than gravity force laterally toa generally vertically oriented column of test sample of whole blood;comprising, a centrifuge head having a peripheral edge and a centralshaft, a driven shaft and a drive motor coupled to said driven shaft forimparting rotative motion thereto, in intermittent periods ofpredetermined duration, said central shaft being mounted to said drivenshaft for free rotation thereabout, independently rotatable sample tubeholder means carried by said head near the peripheral edge thereof, saidsample tube holder means having sample tubes each adapted to contain athin column of blood, said sample tubes being vertically arranged andoriented substantially parallel to the axis of rotation of thecentrifuge head and means for causing periodic rotation of said head athigh speed about its axis and periodic rotation of each sample tubeholder means and the sample tubes therein about its own long axisintermediate the periodic high speed rotation of said head, said lastmeans comprising gear means mounted to said driven shaft for rotationtherewith, said gear means being coupled to said holder means fordriving said heat to rotate the head in said periodic cycles and pin andaperture means operable to limit the extent of rotation of the holdermeans about their own axes.

2. The centrifuge as claimed in claim 1 in which the rotation of saidholders about their own axes for each rotation in one direction islimited to approximately 3. The centrifuge as claimed in claim 1 andtiming means for periodically controlling the duration ofcentrifugation.

4. The centrifuge as claimed in claim 3 wherein said drive motor isreversible and means for exerting gradual braking force at each reversalof motor direction.

5. The centrifuge as claimed in claim 3 in which said drive motor isreversible and said timing means comprise a timing motor, a timing disc,first switch means coupled to said drive motor for deenergizing same,second switch means for reversing said motor, means for coupling saidtiming motor to said timing disc, means on said timing disc constructedand arranged to engage said first switch means after an elapse of timeequal to the total cycle duration and second means on said timing discconstructed and arranged to engage said second switch means periodicallyto reverse the direction of said drive motor, said second means on saidtiming disc being adjustably positioned thereon whereby to determine theinterval between drive motor reversals.

6. The centrifuge as claimed in claim 1 and timing means for controllingthe total duration of centrifugation and the respective cycle durations.

7. The centrifuge as claimed in claim 1 wherein the head is mountedremovably to the driven shaft for rotation thereabout and the gear meansis arranged coaxially relative to said head but for driven rotation withsaid driven shaft.

8. The centrifuge as claimed in claim 1 and timing means forperiodically causing reversal of the direction of rotation of said head.

9. The centrifuge as claimed in claim 1 in which said head is mountedfor removal and replacement as a unit.

10. The centrifuge as claimed in claim 1 in which said gear meansincludes one gear means coupled to the driven shaft and another gearmeans coupled to the sample holder and engaged with said one gear means,and said pin and aperture means comprise a pin mounted on one of saidgear means and head and a substantially circular slot formed in theother of said gear means and head, said pin being disposed within saidslot to limit independent relative rotation of said gear means and head.

11. The centrifuge as claimed in claim 1 in which said gear meanscomprise a spur gear secured to the driven shaft and pinion gearssecured to each respective sample holder and operably engaged with saidspur gear..

12. The centrifuge as claimed in claim 11 in which said pin and aperturecomprise a pin on one of said spur gear and head and an arcuate slot onthe other of said spur gear and head, the pin being received and movablewithin the slot and the length of the slot determining the maximumrotational movement of said pinion gears about their own axes.

13. The centrifuge as claimed in claim 12 in which said motor is of thereversible type, timer means for periodically changing the direction ofrotation of the gear means for each period, said gear means beingarranged to rotate said pinion gears and said head each time the gearmeans is rotated in a new direction.

1. A centrifuge apparatus for studying the sedimentation characteristicsof whole blood by application of greater than gravity force laterally toa generally vertically oriented column of test sample of whole blood;comprising, a centrifuge head having a peripheral edge and a centralshaft, a driven shaft and a drive motor coupled to said driven shaft forimparting rotative motion thereto, in intermittent periods ofpredetermined duration, said central shaft being mounted to said drivenshaft for free rotation thereabout, independently rotatable sample tubeholder means carried by said head near the peripheral edge thereof, saidsample tube holder means having sample tubes each adapted to contain athin column of blood, said sample tubes being vertically arranged andoriented substantially parallel to the axis of rotation of thecentrifuge head and means for causing periodic rotation of said head athigh speed about its axis and periodic rotation of each sample tubeholder means and the sample tubes therein about its own long axisintermediate the periodic high speed rotation of said head, said lastmeans cOmprising gear means mounted to said driven shaft for rotationtherewith, said gear means being coupled to said holder means fordriving said heat to rotate the head in said periodic cycles and pin andaperture means operable to limit the extent of rotation of the holdermeans about their own axes.
 2. The centrifuge as claimed in claim 1 inwhich the rotation of said holders about their own axes for eachrotation in one direction is limited to approximately 180*.
 3. Thecentrifuge as claimed in claim 1 and timing means for periodicallycontrolling the duration of centrifugation.
 4. The centrifuge as claimedin claim 3 wherein said drive motor is reversible and means for exertinggradual braking force at each reversal of motor direction.
 5. Thecentrifuge as claimed in claim 3 in which said drive motor is reversibleand said timing means comprise a timing motor, a timing disc, firstswitch means coupled to said drive motor for deenergizing same, secondswitch means for reversing said motor, means for coupling said timingmotor to said timing disc, means on said timing disc constructed andarranged to engage said first switch means after an elapse of time equalto the total cycle duration and second means on said timing discconstructed and arranged to engage said second switch means periodicallyto reverse the direction of said drive motor, said second means on saidtiming disc being adjustably positioned thereon whereby to determine theinterval between drive motor reversals.
 6. The centrifuge as claimed inclaim 1 and timing means for controlling the total duration ofcentrifugation and the respective cycle durations.
 7. The centrifuge asclaimed in claim 1 wherein the head is mounted removably to the drivenshaft for rotation thereabout and the gear means is arranged coaxiallyrelative to said head but for driven rotation with said driven shaft. 8.The centrifuge as claimed in claim 1 and timing means for periodicallycausing reversal of the direction of rotation of said head.
 9. Thecentrifuge as claimed in claim 1 in which said head is mounted forremoval and replacement as a unit.
 10. The centrifuge as claimed inclaim 1 in which said gear means includes one gear means coupled to thedriven shaft and another gear means coupled to the sample holder andengaged with said one gear means, and said pin and aperture meanscomprise a pin mounted on one of said gear means and head and asubstantially circular slot formed in the other of said gear means andhead, said pin being disposed within said slot to limit independentrelative rotation of said gear means and head.
 11. The centrifuge asclaimed in claim 1 in which said gear means comprise a spur gear securedto the driven shaft and pinion gears secured to each respective sampleholder and operably engaged with said spur gear.
 12. The centrifuge asclaimed in claim 11 in which said pin and aperture comprise a pin on oneof said spur gear and head and an arcuate slot on the other of said spurgear and head, the pin being received and movable within the slot andthe length of the slot determining the maximum rotational movement ofsaid pinion gears about their own axes.
 13. The centrifuge as claimed inclaim 12 in which said motor is of the reversible type, timer means forperiodically changing the direction of rotation of the gear means foreach period, said gear means being arranged to rotate said pinion gearsand said head each time the gear means is rotated in a new direction.